There are a lot of homebrew SSH servers (some free, some paid) out there, but I’ve always stuck to Cygwin’s port of OpenSSH because:
Despite all of its strange properties, I am familiar with Cygwin, ...

Both Interix and Cygwin appear to provide a Unix-like user environment in Windows. What are the practical differences between the two, in terms of, for example:
Unix-like "feel"
Performance
Package ...